CCC 953 Communion in charity. In the sanctorum communio, “None of us lives to himself, and none of us dies to himself.”1 “If one member suffers, all suffer together; if one member is honored, all rejoice together. Now you are the body of Christ and individually members of it.”2 “Charity does not insist on its own way.”3 In this solidarity with all men, living or dead, which is founded on the communion of saints, the least of our acts done in charity redounds to the profit of all. Every sin harms this communion.

1 Rom 14:7.
2 1 Cor 12:26-27.
3 1 Cor 13:5; cf. 10:24.